JPH07311987A - Magneto-optical recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium where the polarization noise of a magneto-optical disk is reduced and thermal stability is improved. CONSTITUTION:A first dielectric layer 102 consisting of TaOx is formed on an organic resin substrate 101, a second dielectric layer 103 consisting of SiN is formed on it, and the surface is subjected to sputter etching treatment 104. Also, a recording layer 105 consisting of amorphous magnetic alloy where rare earth metal and iron transition metal are combined is formed on it and the surface is subjected to sputter etching treatment 106. A third dielectric layer 107 consisting of SiN is formed on it and further a reflection layer 108 and a protection layer 109 consisting of AlTi alloy are formed on it. By performing sputter etching of the surface of the recording layer 105, polarization noise can be reduced and recording medium noise can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium such as a magneto-optical disk for recording and rewriting information by a magneto-optical effect, and more particularly to a magneto-optical recording which suppresses polarization noise and has a low noise level. The present invention relates to a medium and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, an optical disk has received attention as one of large-capacity file memories. Among them, a magneto-optical disk has an advantage that it is possible to rewrite recorded information, and therefore a wide range of applications such as a code data file memory and an image file memory are being actively studied in various places. Therefore, with the expansion of such applications, further improvement in recording density and speeding up are expected.

An example of such a magneto-optical disk is shown in FIG. In the figure, a resin substrate 2 such as polycarbonate
01, a first dielectric layer 202 made of SiN is formed, and the surface of the first dielectric layer 202 is sputter-etched 203. In addition, T formed by a combination of a rare earth metal and an iron group transition metal thereon.
Recording layer 2 made of an amorphous magnetic alloy film such as bFeCo
04, and a second dielectric layer 205 made of SiN is further formed thereon. In addition, a reflective layer 206 of Al or the like is formed thereon.

In this magneto-optical disk, as is well known,
Information is recorded as the direction of magnetization in the recording layer 205 by heating with a laser beam or the like in the state where an external magnetic field is applied, information is reproduced by the polarization direction accompanying this direction of magnetization, and a magnetic field in the opposite direction is generated. Information can be erased by adding it.

[0005]

However, the above-mentioned magneto-optical disk has a problem that the medium noise level is large in the low frequency region of the reproduced signal, particularly in the frequency region of 5 MHz or less. Therefore, the jitter of the reproduced signal is large and the window margin at the time of reproducing the signal is narrowed, which hinders the improvement of the recording density. There is also a problem that the thermal stability of the recorded information on the magneto-optical disk is easily lost due to heat and the like.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magneto-optical recording medium in which the polarization noise is reduced to reduce the medium noise level. Another object of the present invention is to provide a magneto-optical recording medium having improved thermal stability. A further object of the present invention is to provide a method of manufacturing a magneto-optical recording medium having a low medium noise level and high thermal stability.

[0007]

A magneto-optical recording medium of the present invention is a recording layer comprising a first dielectric layer, a second dielectric layer, and an amorphous magnetic alloy on an organic resin substrate. The third dielectric layer and the reflective layer are sequentially laminated, and the surface of the second dielectric layer and the surface of the recording layer are sputter-etched. For example, the organic resin substrate is made of polycarbonate, the first dielectric layer is made of TaOx, the second dielectric layer is made of SiN, and the recording layer is made of a combination of a rare earth metal and an iron group transition metal. The third dielectric layer is made of SiN and the reflective layer is made of AlTi alloy.

The method of manufacturing a magneto-optical recording medium according to the present invention comprises a step of forming a first dielectric layer made of TaOx on an organic resin substrate, and SiN made on the first dielectric layer. A step of forming a second dielectric layer, a step of subjecting the surface of the second dielectric layer to a sputter etching treatment, and a combination of a rare earth metal and an iron group transition metal on the second dielectric layer are combined. A step of forming a recording layer made of an amorphous magnetic alloy, a step of subjecting the surface of the recording layer to a sputter etching treatment, a step of forming a third dielectric layer made of SiN on the recording layer, Al on top of the third dielectric layer
And a step of forming a reflection layer made of a Ti alloy. Here, the amount of sputter etching on the surface of the recording layer is in the range of 20Å to 50Å.

[0009]

By performing the sputter etching on the surface of the recording layer, it is possible to reduce the polarization noise and reduce the recording medium noise level. At the same time, it becomes possible to improve thermal stability.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view of the magneto-optical recording medium of the present invention.
On the surface of a polycarbonate substrate 101 having a thickness of 1.2 mm and a diameter of 130 mm, a first layer of TaOx having a thickness of 300 Å is formed.
Is formed on the dielectric layer 102, and SiN is formed on the dielectric layer 102.
And a second dielectric layer 103 having a thickness of 800 Å is formed. The surface of the second dielectric layer 103 is sputter-etched by a thickness of about 7Å, and the sputter etching treatment 104 is performed on the surface.
Furthermore, the thickness of TbFeCoTi is 250 Å
The recording layer 105 is formed, and the surface thereof is sputter-etched by a thickness of 20 to 50Å to perform the sputter etching treatment 106. A third dielectric layer 107 of SiN having a thickness of 320 Å is formed thereon, and a metal reflective layer 10 of AlTi having a thickness of 300 Å is further formed thereon.
8 is formed. A protective layer 109 made of an ultraviolet curable resin is formed thereon.

Each of the layers is formed by using an in-line sputtering device. That is, the first dielectric layer (TaOx layer) 10
2 uses a Ta target, and the target and the substrate 101
At a distance of 15 (cm) and a power density of 8 (W / cm
2) and the gas flow ratio of Ar and O2 is Ar / O2 = 10.
0/55 (SCCM), sputter gas pressure 0.2 (P
A film is formed under the condition of a).

The second dielectric layer (SiN layer) 103 is S
i target was used, the distance between the target and the substrate 101 was 15 (cm), the power density was 8 (W / cm 2), and the gas flow ratio of Ar and N 2 was Ar / N 2 = 100/5.
The film is formed under the conditions of 5 (SCCM) and a sputtering gas pressure of 0.3 (Pa). The surface of the second dielectric layer 103 has a power density of 0.15 (W / cm 2) and Ar = 25.
(SCCM) and the gas pressure is 0.1 (Pa), the sputter etching is performed to about 7Å, and the sputter etching process 104 is performed.

The recording layer (TbFeCoTi layer) 105 is
Tb target and FeCoTi alloy target (Fe
A film is formed by rotating the substrate 101 by a binary DC magnetron sputtering method using Co Ti atm%). At this time, the distance between the target and the substrate is 10 (c
m) and the power densities of the Tb target and the FeCoTi alloy target are 1.5 (W / cm2),
3.0 (W / cm2), Ar = 50 (SCCM),
The gas pressure is 0.14 (Pa). Then, the surface of the recording layer 105 is sputter-etched under the same conditions as the sputter etching of the surface of the second dielectric layer 103 to form a sputter etching treatment 106. However, the etching amount is in the range of 20 to 50Å.

The third dielectric layer (SiN layer) 107 is formed under the same conditions as the second dielectric layer 103.

The metal reflection layer (AlTi alloy layer) 108 is
Using an AlTi alloy target containing 1 Wt% of Ti and using Ar gas as a sputtering gas, the target and the substrate 1
The distance of 01 is 15 (cm) and the power density is 3.0
(W / cm 2) and the gas pressure is 0.1 (Pa). The protective layer (ultraviolet curable resin layer) 109 is formed by applying an ultraviolet curable resin by spin coating.

Here, in order to confirm the effect of the sputter etching treatment 106 formed by treating the surface of the recording layer 105 in the present invention, the samples in which the sputter etching amount was variously changed from 0 to 70 Å To create. Here, eight types of samples were prepared by changing them in units of 10Å. Then, these samples were attached to a magnet hub in a single plate state, and polarization noise was measured. This polarization noise is measured by initializing the sample and then measuring the difference signal output of the MO head detector under the following measurement conditions. In this case, since the reflectance differs due to the difference in the respective sputter etching amounts,
The power during playback is adjusted so that the amount of returned light is constant.

Polarization noise measurement conditions (a) linear velocity (m / sec): 9.4 (b) frequency (MHz): 1.0 to 10.0 (c) reproducing power (mW): 1.0 ~ 1.9 (d) VBW (Hz): 100 (e) RBW (kHz): 30

Further, the thermal stability (ΔC / N) of the recording signal was evaluated for each sample. In this evaluation, after recording a signal on each sample, a magnetic field of 500 (Oe) was applied to the portion from the outside in the information erasing direction, and at the same time, 2.5 (mW) was applied.
This laser beam is irradiated for 3 minutes, and the difference between the reproduction signals before and after irradiation is taken as the evaluation result.

The measurement result of the polarization noise at 1 MHz is shown on the lower side of FIG. Similarly, the evaluation result of the thermal stability is shown on the upper side of FIG. Polarization noise is reduced by 20 Å as the sputter etching amount increases from 0 Å.
The above values are almost constant. On the other hand, the thermal stability does not change even if the sputter etching amount increases from 0 Å, but when it exceeds 60 Å, the thermal stability rapidly increases and the thermal stability rapidly deteriorates.

From the above, the sputter etching amount when performing the sputter etching process 106 is 20Å to 50.
By adjusting to the range of Å, it is possible to obtain a magneto-optical disk excellent in thermal stability while suppressing polarization noise. In particular, by suppressing polarization noise,
It is possible to reduce the reproduction signal jitter on the magneto-optical disk,
The window margin at the time of signal reproduction can be expanded, and the density of the magneto-optical disk can be increased.

Although the above embodiment shows an example in which the present invention is applied to a magneto-optical disk, the present invention can be similarly applied to other types of recording media such as a magneto-optical card. Further, the composition and film thickness of the recording layer, or the composition and film thickness of the other layers are not limited to those in the above embodiment, and can be appropriately changed to obtain a desired magneto-optical recording medium. Is.

[0022]

As described above, the magneto-optical recording medium of the present invention has a structure in which the surface of the recording layer formed on the organic resin substrate is subjected to the sputter etching treatment, thereby reducing the polarization noise and recording. The medium noise level can be reduced and the thermal stability of the recording medium can be enhanced.

Further, in the method of manufacturing the magneto-optical recording medium of the present invention, after the recording layer is formed, the surface of the recording layer is sputter-etched by a required amount to reduce the polarization noise and to improve the thermal stability. It is possible to manufacture a magneto-optical recording medium having a high temperature.

Furthermore, in the method of the present invention, by setting the sputter etching treatment amount on the surface of the recording layer in the range of 20Å to 50Å, it is possible to suitably improve both the reduction of the polarization noise and the thermal stability. Become.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a magneto-optical recording medium of the present invention.

FIG. 2 is a diagram showing the results of measurement of polarization noise and thermal stability of samples of the magneto-optical recording medium of the present invention with different amounts of sputter etching.

FIG. 3 is a sectional view of a conventional magneto-optical recording medium.

[Explanation of symbols]

 101 Polycarbonate Substrate 102 TaOx Layer (First Dielectric Layer) 103 SiN Layer (Second Dielectric Layer) 104 Sputter Etching Treatment 105 TbFeCoTi Alloy Layer (Recording Layer) 106 Sputter Etching Treatment 107 SiN Layer (Third Dielectric Material) Layer) 108 AlTi layer (metal reflective layer) 109 protective layer

Claims (4)

[Claims] 1. An organic resin substrate, a first dielectric layer formed on the organic resin substrate, and a second dielectric formed on the first dielectric layer and having its surface sputter-etched. A body layer, a recording layer made of an amorphous magnetic alloy formed on the second dielectric layer and having its surface sputter-etched, and a third dielectric layer formed on the recording layer. A magneto-optical recording medium comprising a body layer and a reflective layer formed on the third dielectric layer. 2. The organic resin substrate is made of polycarbonate, the first dielectric layer is made of TaOx, the second dielectric layer is made of SiN, and the recording layer is made of a rare earth metal and an iron group transition metal. The magneto-optical recording medium according to claim 2, wherein the magneto-optical recording medium is formed by a combination, the third dielectric layer is formed of SiN, and the reflective layer is formed of an AlTi alloy. 3. A first layer made of TaOx on an organic resin substrate.
Forming the second dielectric layer, forming a second dielectric layer made of SiN on the first dielectric layer, and subjecting the surface of the second dielectric layer to sputter etching. And a step of forming a recording layer made of an amorphous magnetic alloy in which a rare earth metal and an iron group transition metal are combined on the second dielectric layer, and a step of subjecting the surface of the recording layer to sputter etching. And a step of forming a third dielectric layer made of SiN on the recording layer, and a step of forming a reflective layer made of AlTi alloy on the third dielectric layer. Manufacturing method of magneto-optical recording medium. 4. The method of manufacturing a magneto-optical recording medium according to claim 3, wherein the amount of sputter etching on the surface of the recording layer is 20Å to 50Å.